Hydrogen sensors based on Pt-AlGN/AIN/GaN Schottky diode - art. no. 68291R

Pt/AlGaN/AlN/GaN Schottky diodes have been fabricated and characterized for H-2 sensing. Platinum (Pt) with a thickness of 20nm was evaporated on the sample to form the Schottky contact. The ohmic contact, formed by evaporated Ti/Al/Ni/Au metals, was subsequently annealed by a rapid thermal treatment at 860 degrees C for 30 s in N-2 ambience. Both the forward and reverse current of the device increased greatly when exposed to H-2 gas. The sensor's responses under different hydrogen concentrations from 500ppm to 10% H-2 in N-2 at 300K were investigated. A shift of 0.45V at 297K is obtained at a fixed forward current for switching from N-2 to 10% H-2 in N-2. Time response of the sensor at a fixed bias of 0.5 V was also measured. The turn-on response of the device was rapid, while the recovery of the sensor at N-2 atmosphere was rather slow. But it recovered quickly when the device was exposed to the air. The decrease in the barrier height of the diode was calculated to be about 160meV upon introduction of 10% H-2 into the ambient. The sensitivity of the sensor is also calculated. Some thermodynamics analyses have been done according to the Langmuir isotherm equation.

Structure and visible luminescence of ZnO nanoparticles

ZnO nanoparticles were synthesized in ethanolic solution using a sol-gel method. The structural and optical properties were investigated by X-ray diffraction, transmission electron microscopy, UV absorption, and photoluminescence. After annealing at 200 degrees C, the particle size is increased and the peak of defect luminescence in the visible region is changed. A yellow emission was observed in the as-prepared sample and a green emission in the annealed sample. The change of the visible emission is related to oxygen defects. Annealing in the absence of oxygen would increase oxygen vacancies. (c) 2006 Elsevier Ltd. All rights reserved.

Luminescence properties of Er3+ - Doped SiOx films containing amorphous Si nanoparticles

PL properties of Er3+ doped SiOx films containing Si nanoparticles have been studied. Er3+ emission intensity does not depend strongly upon crystallinity of Si clusters. The films can yield efficient Er3+ emission.

Magnetic Properties of FePt Nanoparticles Prepared by a Micellar Method

FePt nanoparticles with average size of 9 nm were synthesized using a diblock polymer micellar method combined with plasma treatment. To prevent from oxidation under ambient conditions, immediately after plasma treatment, the FePt nanoparticle arrays were in situ transferred into the film-growth chamber where they were covered by an SiO2 overlayer. A nearly complete transformation of L1(0) FePt was achieved for samples annealed at temperatures above 700 A degrees C. The well control on the FePt stoichiometry and avoidance from surface oxidation largely enhanced the coercivity, and a value as high as 10 kOe was obtained in this study. An evaluation of magnetic interactions was made using the so-called isothermal remanence (IRM) and dc-demagnetization (DCD) remanence curves and Kelly-Henkel plots (Delta M measurement). The Delta M measurement reveals that the resultant FePt nanoparticles exhibit a rather weak interparticle dipolar coupling, and the absence of interparticle exchange interaction suggests no significant particle agglomeration occurred during the post-annealing. Additionally, a slight parallel magnetic anisotropy was also observed. The results indicate the micellar method has a high potential in preparing FePt nanoparticle arrays used for ultrahigh density recording media.

Optical properties and electrical bistability of CdS nanoparticles synthesized in dodecanethiol

We reported the synthesis of CdS semiconductor nanoparticles using a simple one-pot reaction by thermolysis of cadmium acetylacetonate in dodecanethiol. Optical measurements of the as-obtained CdS nanoparticles revealed that their optical properties were closely related to surface effects. Based upon the cocktail of poly (N-vinylcarbazole) (PVK) and CdS nanoparticles, a bistable device was fabricated by a simple solution processing technique. Such a device exhibited a remarkable electrical bistability, which was attributed to the electric field-assisted charge transfer between PVK and the CdS nanoparticles capped by dodecaethiol. The conduction mechanism changed from an injection-controlled current to a bulk-controlled one during switching from OFF-state to ON-state.

CFCs和PT方程

CFCs问题引来了广泛的研究.本文概述了CFCs问题.对于状态方程，讨论了1982年发表的PT方程。由此进一步比较讨论了RKS 和PR方程，另外总结了立方型方程的通式.这些对CFCs新工质的模拟计算都具有现实价值.

Influence of dielectric properties of a substrate upon plasmon resonance spectrum of supported Ag nanoparticles

Plasmon resonance spectra of supported Ag nanoparticles are studied by depositing the particles on different substrates. It was found that the dielectric properties of the substrates have significant effects on the spectral line shape, except the resonance frequency. Beyond the plasmon resonance band, the spectral shape is mainly governed by the dielectric function, particularly its imaginary part, of the substrate. The plasmon resonance band, on the other hand, may be severely distorted if the substrate is absorbing strongly.

Enhanced photoluminescence of Nd2O3 nanoparticles modified with silane-coupling agent: Fluorescent resonance energy transfer analysis

A liquid laser medium with a lifetime of 492 mu s and a fluorescent quantum efficiency of 52.5% has been presented by stably dispersing dimethyl dichorosilane-modified Nd2O3 nanoparticles in dimethylsulfoxide. Its optical properties and mechanism were investigated and explained by fluorescence resonance energy transfer theory. The calculation result shows that the quenching of Nd-III F-4(3/2)-> I-4(11/2) transition via O-H vibrational excitation can be eventually neglected. The main reason is that the silane-coupling agent molecules remove the -OH groups on Nd2O3 nanoparticles and form a protective out layer. (c) 2007 American Institute of Physics.

Laser irradiation cell photothermal therapy assisted by gold nanoparticles

The strong absorption of gold nanoparticles in the visible spectral range allows the localized generation of heat in a volume of only a few tens of nanometer. The efficient conversion of strongly absorbed light by plasmonic gold nanoparticles to heat energy and their easy bioconjugation suggest that the gold nanoparticles can be used as selective photothermal agents in molecular cell targeting. The selective destruction of alkaline phosphatase, the permeabilization of the cell membrane and the selective killing of cells by laser irradiating gold nanoparticles were demonstrated. The potential of using this selective technique in molecularly targeted photothermal therapy and transfection is discussed.

全固态电流型氧传感器及Pt-Fe复合催化剂的研究

控制电位电解型即电流型气体传感器由于具有检测气体种类多、浓度范围宽、体积小、价格低、测量精度高、可用于现场直接检测等优点，在环境监测与安全生产等领域中得到了广泛应用。本文论述了纳米级铂、碳纳米管负载铂及铂铁催化剂的合成方法，并对其进行了物理化学表征和电化学研究，主要结果如下： 采用柠檬酸钠还原的方法，合成了纳米级铂催化剂。TEM和XRD测试表明，该球形多晶铂的粒径为2－5nm。用此种铂催化剂制备了离子交换膜电极复合体，并组装了全固态电流型氧传感器；在对低浓度氧气进行测试时，具有高的灵敏度、较短的响应时间、较低的底电流和噪声，且响应信号与氧气的浓度呈良好的线性关系。 1．利用空气氧化和硝酸相结合对多壁碳纳米管进行了纯化，并利用1:1的H2SO4-HNO3混酸使其表面羧基化，TEM和CV测试表明多壁碳纳米管达到了纯化和表面官能团化的目的。 2．利用喷雾冷却法制备了多壁碳纳米管负载的铂及铂铁合金纳米级催化剂复合体，并利用TEM、EDS、XRD、ICP等进行了表征；在循环伏安扫描中，铂铁合金催化剂呈现较高的比表面积。将多壁碳纳米管负载的铂及铂铁合金纳米级催化剂应用于C1有机小分子的电化学氧化研究中发现，铂铁合金催化剂具有较高的催化活性.